Codeigniter -未定义属性$grocery_crud

非常 Codeingiter新手，并试图实现杂货CRUD以下本教程http://www.grocerycrud.com/documentation/create-crud-codeigniter-tutorial。

在下面的代码中这样做了(顺便说一下，我正在自动加载数据库库和url helper)。

<?php
class Management extends CI_Controller {

public function construct()
{
    parent::__construct();
    $this->load->library('grocery_CRUD');
}
public function index ()
{
    echo "<h1>Just work!</h1>";
    die();
}

public function property ()
{
    $this->grocery_crud->set_table('property');
    $output = $this->grocery_crud->render();

    echo "<pre>";
    print_r($output);
    echo "</pre>";
    die();
}

/**
public function view($page = 'management_page')
{
    if ( ! file_exists('application/views/pages/'.$page.'.php'))
    {
        // Whoops, we don't have a page for that!
        show_404();
    }

    $data['title'] = ucfirst($page); // Capitalize the first letter

    $this->load->view('templates/header', $data);               
    $this->load->view('pages/'.$page, $data);
    $this->load->view('templates/footer', $data);
}
**/
}

然而，当我在[BASE]/management/property加载此页面时，我得到以下错误:

Severity: Notice
Message: Undefined property: Management::$grocery_crud
Filename: controllers/management.php
Line Number: 21

有人能帮忙吗?